Operation system monitoring is a key component of any large scale software system, such as an enterprise database server. In such complex systems, the ability to monitor in-memory operational metrics provides critical diagnostic capabilities that allow administrators to determine whether the system is operating properly, and to help diagnose potential problems in system operation when it is not. Such monitoring capabilities are often complex, involving the collection of numerous metrics by individual execution threads in the system, and the accumulation and reporting of those metrics along various dimensions. For example, in a database server system, monitoring capabilities might provide reporting of accumulated in-memory metrics per connection, per transaction, per statement, per service class, and per database. One challenge in the design and implementation of any such monitoring capability is providing timely operational metrics while keeping the performance impacts on the system low. The desirable characteristics of a monitoring capability includes: low collection overhead, low query overhead, and real time or near-real time operational metrics on the system. In any typical software system, the monitoring capabilities must make tradeoffs in one or more of these categories to achieve advantages in the others.